David Cameron has hailed the reopening of the storm-wrecked railway line at Dawlish in Devon on Friday as a great day.

After weeks of work by a 300-strong team, Network Rail (NR) has been able to restore the badly damaged line, which had cut off rail services to the south-west of England. Businesses in Devon and Cornwall have estimated that the line's closure was costing the regional economy £20m a day.

Writing in the Western Morning News, the prime minister said the line, which was left suspended in mid-air above a smashed sea wall, had become "one of the defining images of this winter's storms".

"I went to see the damage for myself. It looked like something from a disaster film. But for the people of Devon and Cornwall, this was real life – and a massive blow to commuters, businesses and the tourist industry," he wrote. "Today's reopening says loudly and clearly: the south-west is back open for business."

The damage to the coast-hugging line at Dawlish on 4 February led to the closure of the line linking Exeter St Davids with Newton Abbot, Plymouth and Penzance and left NR facing a major repair job.

The work was hampered by another severe storm on the night of 14-15 February when rough seas battered the 10-tonne shipping containers forming a temporary sea wall. The storm damaged a further 10 to 20 metres of the actual sea wall and more shipping containers had to be moved in.

There were further problems on 4 March when engineers discovered that 20,000 tonnes of cliff face near Teignmouth, south of Dawlish, had sheared away above the railway. This meant stabilisation work had to be done.

With teams working around the clock, NR was able to bring the line reopening date forward two weeks, enabling the line to be open in time for the Easter holidays.

Repair work has included:

• The building of a temporary sea wall from 18 welded shipping containers to protect homes and engineers as they worked to repair a 100-metre breach at Riviera Terrace, Dawlish, following the February storms;

• The rebuilding and fortification of the breach, with more than 6,000 tonnes of concrete and 150 tonnes of steel;

• The removal of 25,000 tonnes of collapsed cliff at Teignmouth;

• The repair of dozens of other sites along a four-mile stretch of coastal railway, clearing hundred of tonnes of debris and repairing more than 600 metres of parapet wall;

• The rebuilding of half of Dawlish station with a new platform, new canopy and repainting throughout;

• The installation of more than 13 miles of new cables, the design and installation of a temporary signalling system and replacement of more than 700 metres of track and ballast.

The NR chief executive, Mark Carne, said: "Our army of engineers has done an amazing job of putting back together a railway that was ravaged by the elements.

"They have overcome every obstacle thrown at them, winning many battles along the way to restore this critical piece of the network, ahead of schedule, and in time for the Easter holidays."

He added: "The biggest thanks must be reserved for passengers and local communities and businesses who have been hugely supportive and patient over the past two months as we worked flat out to rebuild this vital rail link.

"Our focus now moves to the medium- and long-term, looking at what can be done at Dawlish to make the current coastal route more resilient and, by the autumn, understand what the best viable relief route might be."